Study On Thermal Efficiency Of Vacuum Hot Water Boiler

With the continually innovation of the energy policy and energy structure of our country, the natural gas will become the primary source of energy in large and medium cities, the application of gas vacuum hot water boiler will be more extensive. Complying with the national environmental protection policy and having multi-functional, there will be a wide application prospect for the gas vacuum hot water boiler.Because of the high thermal efficiency, environmental protecting, safe and reliable operating, free erection site, little investment for the first time, and the low operating cost, the gas vacuum hot water boiler has gradually replaced the traditional coal-fired hot water boiler in some large and medium cities.Vacuum hot water boiler utilizes phase change principle to operate. Under the operating pressure, which is below atmospheric pressure, hot medium water is boiled. The supplying water is heated by steam in boiler, and is sent to users. Hot medium water is condensed into boiler to complete this cycle process.This thesis has researched the vacuum hot water boiler, which is developed by Shengyuan Central Air-conditioning CO., LTD affiliated with Tianjin University, analyzed the operation principle and heat transfer characteristics of it, calculated the vacuum hot water boiler thermal efficiency, and done the experimental study. This research includes the process of fuel combustion, the heating transfers process of water in boiler. Through the CFD simulation, the distribution of temperature inside the boiler was obtained. This study results will guide the design of gas vacuum hot water boiler.The heat transfer in the gas vacuum hot water boiler is large space boiling. The coefficient of heat transfer in boiling is calculated, through the analysis of principle of heat transfer in boiling. The process of water heat transfer in heat exchanger is film condensation heat transfer, and the condensation coefficient of heat transfer is gotten by the formula of laminar film condensation heat transfer. The effective factors of condensation heat transfer outside the tubes are analyzed. Finally, the process of heat transfer is calculated in the furnace, smoke tube and condensation heat transfer tube, and the design of construction is checked out. In the experiment, the thermal efficiency of this boiler is up to 93%.